Simple determination of the systolic–diastolic pressure relationship from blood pressure readings taken at different arm heights

Abstract

The slope of the linear relationship between systolic blood pressure (SBP) and diastolic blood pressure (DBP) determined from 24-h ambulatory measurements incorporates clinical and prognostic information and is believed to reflect arterial properties. We evaluated the feasibility of determining a similar relationship using the gravity-induced brachial blood pressure (BP) variation in response to vertical cuff displacement with reference to the heart. Nine consecutive BP readings were taken in the sitting position with arm postures stabilized by a mechanical support and with the cuff positioned at four different measured heights. The SBP-on-DBP slope (dS/dD) was estimated on the basis of the SBP and DBP variability ratio and expressed in terms of SD. The test was applied to 30 unselected volunteers (52% men, age 48±14). A mean cuff elevation of 32 cm was associated with a BP reduction of 21/19 mmHg (P<0.00001) without changes in the heart rate. The SBP-DBP correlation was 0.94±0.03 and the dS/dD was 1.10±0.03, with a determination error of 13±4% (mean±SE). Our results were similar to those of a previous study (n=37) having the same protocol, but in which the arm was self-supported. A case report that included 20 dS/dD determinations over 5 consecutive days and nights without height measurements demonstrated the repeatability of dS/dD, with a mean test duration of 13 min. The present study provides a novel, simple, and rapid method of attaining vascular-related information and its variation over time from BP measurements, with good accuracy that is applicable to both office and home. However, comparability with the ambulatory method, prognostic significance, and outcome variation over time remain to be evaluated.